Washington, DC -- December 10, 2013 --Eslicarbazepine acetate (ESL), a sodium-channel blocker and oral antiepileptic drug (AED) designed to be taken once daily, is a safe and tolerable adjunctive treatment for partial-onset seizures, according to a study presented here at the 67th Annual Meeting of the American Epilepsy Society (AES).

Bassel Abou-Khalil, MD, Vanderbilt University Medical Center, Nashville, Tennessee, presented the findings of the phase 3 study on December 8.

The trial comprised 653 patients from 173 centres. Inclusion criteria were age ?16 years, occurrence of ?4 partial-onset seizures during a 4-week period, and medication with 1 or 2 AEDs.

The ESL doses initially began lower and were ramped-up during a 2-week double-blind titration phase, followed by a 12-week fixed-dose maintenance phase. The patients then entered a 12-month open-label extension or were tapered off the drugs over a 2-week period. The intention-to-treat group of 640 patients received ?1 postbaseline seizure frequency assessment. A total of 504 patients completed the double-blind portion of the trial (placebo, n = 189, 84%; ESL 800 mg, n = 173, 80%; ESL 1,200 mg, n = 142, 67%).

Standardised seizure frequency every 28 days during the maintenance phase was the primary endpoint. The secondary endpoint was the proportion of patients with a ?50% reduction in standardised seizure frequency compared with baseline. Safety endpoints included adverse events, clinical laboratory results, vital signs, body weight, and electrocardiogram readings.

Patient demographics were similar among study arms. Also, the arms were similar in the duration of epilepsy, frequency of seizures in the 4 weeks preceding trial screening, standardised seizure frequency during baseline, seizure type, and AED type and prevalence during baseline.

The least-squares mean standardised seizure frequency during the maintenance phase was 7.88 with placebo, 6.54 with ESL 800 mg (<i>P</i> = .058), and 6.00 with 1,200 mg (<i>P</i> = .004). The secondary endpoint (responder rate) was reached in 23.1% of patients in the placebo arm, 30.5% of patients in the ESL 800-mg arm, and 42.6% of patients in the ESL 1,200-mg arm.

The overall incidence of all treatment-emergent adverse events (TEAES) and TEAEs considered at least potentially related to treatment tended to increase with increased ESL dose. Most TEAEs were mild to moderate. TEAEs occurred in 55.8% of patients in the placebo arm, 67.1% in the ESL 800-mg arm, and 77.6% in the ESL 1,200-mg arm. The most common TEAEs were dizziness, somnolence, nausea, headache, and diplopia.

More patients reported serious AEs with placebo (3.1%) and ESL 800 mg (6.5%) than with ESL 1,200 mg (1.4%). One death occurred during baseline. Two patients died during the titration and maintenance phases of the study: 1 in the placebo arm from acute respiratory failure and 1 in the ESL 800-mg arm attributed to status epilepticus.

With the exception of serum sodium, which was reduced in the ESL groups at 8 weeks compared with baseline levels, changes in clinical laboratory parameters were not appreciably different for the 3 arms throughout the trial.

In this phase 3 study including a large North American subpopulation, ESL 800 mg and 1,200 mg once daily were generally well tolerated in patients with refractory partial-onset seizures, concluded the researchers.

ESL was approved in 2009 by the European Medicines Agency as adjunctive therapy in adults with partial-onset seizures. The results presented herein, combined with efficacy results from 2 other phase 3 trials, led to the recent approval by the US Food and Drug Administration.